In a damper, a piston rod and a piston are able to move within a chamber which may, for example, be filled with oil, separated by the piston into an upper chamber and a lower chamber. The piston is able to move between a compression position and an expansion position. In the compression phase the oil passes from the lower chamber to the upper chamber and in the expansion phase the oil passes from the upper chamber to the lower chamber. In the compression phase the piston rod and the piston move down into the chamber and thus reduce the available volume inside this chamber. Some of the oil thus needs to be evacuated from the chamber to compensate for the increase in volume of the piston rod in the chamber. In the compression phase the piston moves down into the chamber.
To this end a compensation chamber is provided which surrounds the upper and lower chambers and permits surplus oil to be evacuated from the lower chamber in the compression phase. In the expansion phase the piston rod and the piston move back up in the chamber and thus increase the available volume inside this chamber. Some of the oil in the compensation chamber goes back into the chamber to compensate for the decrease in volume of the piston rod in the chamber.
In order to allow the oil to flow between the compensation chamber and the lower chamber, a valve assembly is provided to control this flow. This valve assembly may, for example, include a valve sliding in a valve holder and a base intended to be supported on the bottom of the damper.
In known valve assemblies, the elastic holding device is fixed to the foot of the valve holder on the one hand and inserted into a groove provided on the upper surface of the base on the other hand. In the expansion phase, the holding device becomes deformed due to the partial vacuum created by the lack of oil in the lower chamber and is pressed against the groove, which “pulls” on the base.